The present invention relates to an insulated vessel which may be produced at low cost, has superior insulating capabilities and excellent volumetric efficiency, and which may be suitably employed in a thermos, cooler, icebox, insulated cup, thermal insulated lunch box, thermal insulated electric pot, heat retaining rice cooker, refrigerator or freezer box material, or as an insulating layer in a bath tub.
Insulated vessels are conventionally available having a double walled structure wherein the space interval between the outer vessel and the inner vessel is filled with an organic foaming material such as hard urethane foam or foaming polystyrene, or a fabrication thereof, or is filled with an inorganic powder such as perlite.
Also conventionally available is a vacuum insulated vessel wherein the space between the inner vessel and the outer vessel of a double walled vessel consisting of a metallic inner vessel and a metallic outer vessel joined in an integral fashion is vacuum sealed to form a vacuum insulating layer.
However, in the former insulated vessel, because the coefficient of thermal conductivity of the insulating material itself is large compared to the case of a vacuum insulation, it is not possible to obtain a high degree of insulating capability. Further, problems also exist with respect to the production and capabilities of this vessel in that, because it is necessary to make the insulating layer thick (more than several centimeters) the vessel has a small ratio of inner volume to the outer volume. That is to say, volumetric efficiency is reduced.
Furthermore, while the latter vacuum insulated vessel has excellent insulating capabilities, an insulating layer of a small thickness, and large volumetric efficiency, the production process is complicated. Accordingly, high production costs are incurred.
The present invention was conceived in consideration of the aforementioned problems, and has as an object the provision of an insulated vessel which has excellent insulating properties, is light, and for which it is possible to achieve a high volumetric efficiency.
The insulated vessel of the present invention has a double walled structure wherein an inner vessel and an outer vessel have been joined in an integral fashion, with the space interval therebetween being filled with a low thermoconductive gas consisting of at least one of xenon, krypton and argon. Furthermore, in the present invention, a metallic heat radiation preventing material is disposed at least one of the outer surface of the inner vessel and the inner surface of the outer vessel.
The aforementioned heat radiation preventing material is selected from a metallic foil disposed in the aforementioned space interval, or a metallic film provided at at least one of the outer surface of the inner vessel or the inner surface of the outer vessel.
The space interval between the inner vessel and the outer vessel of the double walled vessel in this insulated vessel is preferably between 1 and 10 mm thick.
Furthermore, the insulating layer may be constructed as a plurality of layers by disposing in the space interval between the inner vessel and the outer vessel one or more partitioning members which partition the insulating layer in the direction of the thickness thereof. The space interval of the respective partitioned insulating layers is preferably in the range of 1 to 10 mm.
Furthermore, the filling pressure of the low thermoconductive gas which fills the space between the inner vessel and the outer vessel of the double walled vessel of the present invention is preferably 740-780 mmHg at room temperature.
The method for producing the insulated vessel of the present invention comprises the steps of:
preparing a double walled vessel wherein an inner vessel and an outer vessel are joined in an integral fashion, an opening is provided to either the inner vessel or the outer vessel, and a metallic heat radiation preventing material is disposed between the outer surface of the inner vessel and the inner surface of the outer vessel;
evacuating the air from the space interval between the inner vessel and the outer vessel via the opening of the double walled vessel;
filling the space interval with a low thermoconductive gas consisting of at least one of xenon, krypton and argon; and
sealing the opening of the double walled vessel.
The aforementioned heat radiation preventing material is selected from a metallic foil disposed in the space interval, or a metallic film provided at at least one of the outer surface of the inner vessel and the inner surface of the outer vessel. The aforementioned opening provided to the double walled vessels is selected from an evacuation hole or an evacuation tube.
In this production method, preferable as the method of production for the double walled vessel are the following methods:
a) A method wherein a cylindrical inner vessel having a bottom and a cylindrical outer vessel are attached in an integral fashion at the mouth portions thereof, a metallic heat radiation preventing material is disposed between the outer surface of the inner vessel and the inner surface of the outer vessel, and a bottom plate having said opening is joined to the open bottom of the outer vessel.
b) A method wherein a cylindrical inner vessel having a bottom and a cylindrical outer vessel, having a bottom which has said opening, are prepared, a metallic heat radiation preventing material is disposed between the outer surface of the inner vessel and the inner surface of the outer vessel, and the inner vessel and the outer vessel are joined in an integral fashion at the mouth portions thereof.
c) A method wherein a configured double walled structure is prepared with the mouth portion for a cylindrical outer vessel and a cylindrical inner vessel having a bottom being formed in an integral fashion using an integral double molding method, a metallic heat radiation preventing material is disposed to at least one of the outer surface of the inner vessel and the inner surface of the outer vessel, and a bottom plate having said opening is joined to the open bottom of the outer vessel.
It is preferable that the pressure difference between the space interval and the environment outside the double walled vessel be small or nonexistent when carrying out the step for evacuating the air in the space interval between the inner vessel and the outer vessel of the double walled vessel and the step for filling with the space with the low thermoconductive gas.
In the insulated vessel of the present invention, the insulating layer is formed by filling the space interval between the inner vessel and the outer vessel of the double walled vessel with a low thermoconductive gas consisting of at least one of xenon, krypton and argon, and disposing a metallic heat radiation preventing material in the insulating layer. As a result, the present invention has markedly improved insulating capabilities as compared to conventional insulated vessels wherein the space between the inner vessel and the outer vessel is filled with an organic or inorganic solid insulating material. Furthermore, because the present invention does not employ the technique of filling with a solid insulating material, it is possible to make the insulated vessel lighter. Moreover, as compared to conventional vacuum insulated vessels, the pressure difference between the insulating layer and the outside in the present invention is small so that, accordingly, the pressure strength demanded of the double walled vessel is also small. As a result, it becomes possible to increase the degree of freedom permitted with respect to the shape and material of the double walled vessel. Furthermore, the volumetric efficiency of the insulated vessel is improved. Accordingly, by means of the present invention it becomes possible to offer an insulated vessel which has superior insulating capabilities, is light, and has high volumetric efficiency.
Moreover, by setting the thickness of the insulating layer to be between 1 and 10 mm, convection of the filler gas is controlled, thus obtaining excellent insulating effects.
By disposing one or more partitioning members which partition the insulating layer along the direction of its width in the space interval between the inner vessel and the outer vessel a plurality of insulating layers is formed. As a result, an insulated structure identical to that in which a plurality of insulating layers are layered on top of one another is obtained, making it possible to obtain even more excellent insulating properties.
Furthermore, by setting the filling pressure of the low thermoconductive gas to be 740-780 mmHg at room temperature, the pressure difference between the insulating layer and the outside when pouring in cold or hot liquids is small and the atmosphere pressure applied to the double walled vessel is reduced. The pressure strength required of the vessel is reduced, and the vessel can be made more lightweight. Moreover, it is possible to further increase the degree of freedom permitted with respect to the design and material of the vessel.
Moreover, in the production method for the insulated vessel of the present invention, a double walled vessel wherein a metallic heat radiation preventing material is disposed at, at least one of either the outer surface of the inner vessel or the inner surface of the outer vessel is produced. The air in the space interval between the inner vessel and the outer vessel is evacuated via an evacuation hole or an evacuation tube in the double walled vessel, and this space interval is then filled with a low thermoconductive gas. The opening of the evacuation hole or the evacuation tube is sealed, obtaining an insulated vessel having excellent insulating properties. The production steps are simple and easy. Moreover, because production using a synthetic resin material which is easily formable is also possible, it is possible to reduce production costs.
Furthermore, if a metallic foil is used as the heat radiation preventing material, a lower cost production as compared to one employing the technique of plating the surfaces of the inner and outer vessels which face the insulating layer can be realized.
Moreover, by using a heat radiation preventing material consisting of metallic foil, the double walled vessel and the metallic foil are easily recyclable. Accordingly, the present invention is advantageous both from the perspective of low production cost and conservation of resources.
Moreover, by making the pressure difference between the space between the inner vessel and the outer vessel and the outside small when carrying out the steps of vacuum evacuating this space and filling it with a low thermoconductive gas such as xenon, it is possible to prevent the application of external force arising from a pressure difference on the double walled vessel. Even when employing a double walled vessel which has almost no pressure proof structure, no dents are created in the vessel, and it is possible to sufficiently evacuate the inside. As a result, the degree of freedom permitted with respect to the design and material of the vessel is increased, and the vessel can be made even more lightweight.